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John Wheeler - Session VII
John Wheeler - Session VII
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Interview of John Wheeler by Kenneth W. Ford on 1994 February 14,
Niels Bohr Library & Archives, American Institute of Physics,
College Park, MD USA,
For multiple citations, "AIP" is the preferred abbreviation for the location.
This is one of 22 sessions of oral history interviews with John Archibald Wheeler conducted by Kenneth W. Ford between December 6, 1993 and May 18, 1995. They represent research material for Wheeler’s autobiography, Geons, Black Holes, and Quantum Foam: A Life in Physics (Norton, 1998).
John Wheeler talks about his thoughts on action-at-a-distance during his war work.
BASIC RESEARCH DURING THE WAR
I didn't have the imagination to appreciate how decisive the fission work could be in the war. I felt that in the long haul what would count more was understanding the foundations of physics. To me, psychologically, action-at-a-distance as a way of describing the interaction between particles seemed more direct and more natural than field theory. That's how come I spent so much time with Feynman on action-at-a-distance as a way of understanding the coupling between charged particles, but we did not have time to finish up that work before we were separated by my having to go to Chicago. It was not until 1945 that we had a chance to finish up the work.
GEARING UP FOR WAR WORK
Ford: The previous narrative got us up through about the middle of 1939, the work with Niels Bohr on fission.
By this time Wigner had been caught up in the enthusiasm of Szilard for making a nuclear chain reaction. Wigner was treating the theory of the multiplication factor, including all the natural physical effects—the initial travel of the neutron from the point of fission out into the surrounding moderator, and then the successive steps in the moderation. At that time Fermi used the word "slower downer." I'm afraid that got under my skin so much that I found myself forced to invent a word that would be more reasonable. That's how come the word "moderator."
There were factors in this calculation of Wigner's that it was hard to deduce purely by theory. The biggest source of uncertainty, if I remember it correctly, was the behavior of neutrons in the intermediate energy range between the MeV level and the thermal level — how far would they travel in that region? To answer questions of that kind, Wigner got the cyclotron group busy. Milt White was the head of the cyclotron group, but Edward Creutz was a real live wire in it, and he was a real pusher. He was ready to sweep floors or do anything it took to get the job done. That was true in his later work at the Chicago laboratory where he realized that metallurgy of uranium was very important; he visited companies that might be able to supply the technology to make good uranium. I can recall going with him and the sales talk he gave to the company we visited somewhere in Ohio about the importance of doing this.
At this time, various people were being sucked away from the Princeton Physics Department to take part in the work of the MIT Radiation Laboratory, which was appealing to many physicists who had worked with the design of cyclotrons. The idea of a cavity, the idea of an oscillating electromagnetic field, all these were common features of the two enterprises of the cyclotron and the Radiation Laboratory.
The sound of the war was coming closer. Every day's headlines had to do with battlefronts. There was a radio in the room where the tea was served, and often we would go there to catch the latest news. The horrors of concentration camps I can't recall appearing in the paper. On the contrary, the efficiency of the Germans was very apparent, and I confess that to the horror of my family I came to the conclusion that Europe would never be at peace until it was under the control of one power, and I saw no likely candidate for that power but Germany. Being a member of the German Physical Society, I also received automatically some German propaganda paper, and my family felt that this was disreputable.
BASIC RESEARCH DURING THE WAR
I didn't have the imagination to appreciate how decisive the fission work could be in the war. I felt that in the long haul what would count more was understanding the foundations of physics. To me, psychologically, action-at-a-distance as a way of describing the interaction between particles seemed more direct and more natural than field theory. That's how come I spent so much time with Feynman on action-at-a-distance as a way of understanding the coupling between charged particles, but we did not have time to finish up that work before we were separated by my having to go to Chicago. It was not until 1945 that we had a chance to finish up the work. We did it on the occasion of visits I made to Los Alamos, and we were helped by the existence of deadlines: the deadline for a paper for an Einstein anniversary and a deadline for a paper for a Bohr anniversary.
The general idea [of action at a distance] is described in our paper of 1945. As to the second paper, in 1949, it was especially interesting to us to be told by Einstein when we called on him that he had felt that the limitation of ordinary electrodynamic analysis to retarded potentials was not one of fundamental physics, not due to anything in the basic interaction between particles, but due to the statistics—the kind of phenomenon that makes heat spread. I can't recall whether we tried out on him the final wording that we developed after we had talked with him, but it is clear that the idea that you only get the well-tested law of radiative reaction when you have enough particles at a distance to give complete absorption—that was a spelling out of his idea that the one-sidedness in time of electrodynamic interactions as one ordinarily takes it to be was not a fundamental thing but one based on the existence of large numbers of particles.
I don't know how come Dirac was around at the time Feynman and I were doing our work, but I do know that it was a vital factor in Feynman's coming to a good way to treat electrodynamic interactions in the framework of quantum theory for him to read a paper of Fermi on the role of the Lagrangian in quantum mechanics. He had already come to what I like to call the idea of sum over histories before we were forced by the war to separate. That was the stimulus for me to go tell Einstein about it and describe it in maybe twenty minutes, and me ending up by saying, "Professor Einstein, doesn't this make you feel it's completely reasonable to accept quantum mechanics?" But he didn't swallow that and said he still couldn't believe that the good Lord plays dice. But he went on to add, "Maybe I have earned the right to make my mistakes."
I can't recall Feynman and myself writing letters to each other during the war. We depended on visits for any contact on these questions.
Ford: The fact that you published a significant paper in 1945 must mean that you were able even during your work on the Manhattan Project to keep your hand in with some basic physics.
I think it was one more instance that I can't get anything done unless there's a real pressure, [ laughs ] And a visit to Feynman was always a pressure. A visit to anybody on an idea that he and I share, there's always a pressure to push ahead.
OTHER PHYSICS BEFORE WAR WORK STARTED
Barschall and I did a paper in 1940 on the scattering of neutrons in helium. The machine in the attic of Palmer Laboratory was an enormous help, because it gave neutrons of an energy that could be adjusted over a certain region. To have scattering cross section as a function of angle, I had already provided a way to determine so-called phase shifts of quantum mechanical wave functions for this, that, and the other angular momentum, and from that to get some idea of the interaction responsible for this phase shift in the wave function. In a later paper Barschall points out that our work really amounted to the first evidence for the spin-orbit coupling which Maria Mayer and Jensen were to invoke for explaining the order of filling of energy levels in the nucleus. I don't recall when that paper [ Barschall's ] came out. I would say perhaps in the last ten years—that is perhaps since 1980. His having those results right then and there gave an occasion right then and there to do the analysis, which was an encouragement to go back to an analogous problem—not the scattering of neutrons in helium, but the scattering of alpha particles in helium, which I had started working on already at the time of the London International Conference. To have some results on the coupling between one alpha particle and another and to have the idea of a kernel, an integral kernel—that is to say, a velocity-dependent potential—that's a feature of this coupling giving encouragement to furthering what could be done with the alpha particle model of nuclei. The simplest example is the nucleus beryllium 8.
I'm not sure whether there were two mesons at this time or just one, but there was real interest in the question what is the mass of the cosmic-ray meson. Rudolph Ladenburg, my older colleague, and I found ourselves asking about ways to measure the mass of the meson, and concluding that one way to do it was to measure the curvature produced in the track by a magnetic field before and after the meson had gone through a lead plate. The curvature gives directly the momentum, so that one's measuring the loss of momentum. But how much loss of momentum takes place depends on the mass of the particle.
Ford: Did Ladenburg actually conduct such experiments, or was this just a theoretical paper?
This was just a theoretical paper, to the best of my memory. I suspect that Ladenburg had the thought that his group might well do something in this direction.
Rupert Wildt in the astronomy department talked to me at one time about the spectrum of certain stars where he felt anomalies could be understood possibly by the presence of negative hydrogen ions there. So, how would a negative hydrogen ion affect the spectrum coming from the star? He and I found ourselves led into analyzing the absorption coefficient of the negative hydrogen ion in transition from one free state to another. The type of analysis involved is very similar to the work I had done for my Ph.D. thesis on the absorption of light by helium. That is: in both cases the two-electron system; in both cases, the effect of radiation on this two-electron system.
EARLY REACTOR WORK
I see in my bibliography a paper with Bob Christy of January 1943 on the subject of chain reaction of pure fissile materials in solution. I can believe that that was motivated by the concern already being felt by my Du Pont friends for the safety of processing plutonium. The design had not yet been completed for the plant where the chemical separation of plutonium was to be done.
OTHER BASIC PHYSICS BEFORE AND DURING THE WAR
I realize that I left off on this discussion of work on scattering and phase shifts and the work done at Princeton in that area before I had mentioned Malcolm McPhail, the Canadian who worked with Ladenburg's group. There was some set of measurements he had made before the method of phase shifts came into use. I can recall discussing this with him. We did not write a paper together, so I would have to look up his name in the Physical Review to find out exactly what it was he did. Janette and I visited him in later years after he had retired. He had retired various times—retired from Princeton, retired from Rice University—and he was living in the little town of Ajijic in the State of Jalisco in Mexico, on the shore of Lake Chapala. Liking beautiful parts of nature, he also ended up getting property on an island near Victoria, British Columbia in later years. He's now no longer living.
On the early Manhattan Project...
Ford: John, before getting into that, could I insert one question related to your work with Feynman? In his Nobel speech, he gives you credit for the idea of a positron being an electron moving backward in time. That's a very exciting idea. Do you recall the circumstances that led you to that idea, or when it was?
No, I can't. I certainly recall my excitement at the idea, and calling him up one evening at the Graduate College to say to him that there's only one electron in the world going forward and backward in time. I had written, while I was at New York with Gregory Breit, a paper on the production of a pair of electrons out of a vacuum by the collision of two photons, and it was natural to try to think of a way to picture that in terms of direct interaction between particles—the particles that produced the photons. But then what about the effect on the electron? The direct picture which I had become so accustomed to using was of a positron being produced by raising an electron out from a negative energy state and producing a vacancy in that negative energy state—a vacancy that behaved as if it had a positive charge. It was all in the spirit of keeping ideas simple to change from talking about a vacancy in a negative energy state to a particle going backward in time in a positive energy state. I can't recall the detailed genesis of that idea.
MANHATTAN PROJECT—EARLY REACTOR WORK
I came across recently—speaking of the Manhattan Project—an article by Dale Babcock of Du Pont about some of my involvement in it. I certainly was interested when I went to Chicago at the end of January 1942 in getting on with this business of making a production reactor, a reactor to produce plutonium. Louis Turner's marvelous idea that not only is plutonium fissile, as one could see from the curve that Bohr and I published, but also it would be something easy to separate, or relatively easy to separate, from uranium. Someone [ ? ] would overcome the terrible problem of isotope separation, which stood in the way of using uranium 235, the only fissile material that had been considered for weapons up to this time.
I did not really get involved in figuring out how to make a bomb, but I can recall a visit of a British group of three men to the Chicago project in the summer of 1942 in which they said if you are working on this to make power or drive submarines, forget it; that won't contribute to this war. We are being bombarded in London right now. The only thing that will get things done is to make a bomb. The people on that committee were Sir John Simon and Sir Wallace Akers, who was head of Imperial Chemical Industries... I don't recall at the moment the third person. Oh, I think Sir John Cockcroft.
A difference of opinion arose along in the early summer of '42 as to the right way to cool the reactor. The idea that had been current up to that time was cooling by helium, a substance that would not absorb neutrons. Wiener had the vision and courage to recognize that water was a much better heat transfer medium and it was conceivable that the water would not absorb too many neutrons, so that it could be used. I was not very keen on chancing water, and I can recall running an experiment in the lab zooming not helium but air through a channel in the graphite block to see how much erosion there would be, because foes of gas cooling cited the possibility that the high velocity of gas flow would strip particles from the graphite and gradually erode the channel, erode the pile away. That measurement that I made was favorable to using helium, but the continual improvement in the chemical quality of the uranium that was being used, freeing it from impurities, kept bringing the multiplication factor up to a point where there was enough to overcome the absorbing properties of water.
WORKING WITH DU PONT
The Stone and Webster Company supplied an engineer, who had been asked by Arthur Compton, the director of the Chicago laboratory, to get going on plans for a plant, a plutonium production plant. This engineer found so much negative attitude toward the helium that Compton had told him to put in that he had trouble getting anybody to collaborate with except me. So I guess I acquired a reputation as somebody who could get along with engineers. At any rate, Stone and Webster had to drop out and General Groves picked Du Pont to run the project. It must have been Compton that suggested that they ask me to come and be on hand to answer questions that might come up. In the beginning that looked like a temporary business, but as the weeks went by I was spending more and more time in Wilmington. I guess once a week I'd go back and forth on the train between Wilmington and Chicago.
I think it was Thanksgiving Day, 1942, while the pile was being made ready in the West Stands for the proof that it would work. I was sitting with Du Pont colleagues around the table going over possible sites where the plant might be located. I forget whether it was Florida or South Carolina that looked attractive because of water supply and isolation. One factor that I got my friends to dig up was how many thunderstorm days there are per year that might knock out the electrical power supply to run the pumps to pump water through the plant, and that was how come we struck out the site in South Carolina or Florida, whichever way it was. They had too many thunderstorm days per year.
We ended up with the site in the State of Washington. I had never realized until I got there that there was this desert country in the middle of the State of Washington, as the Cascade Mountains scraped, in effect, the water out of the air coming from the Pacific. That water ran down the western slopes of the Cascades, but on the eastern side it was really dry—eight inches of water fall per year. There was this huge site there with only a few farmers who depended upon pumping irrigation water from the Columbia River to keep going—fruit orchards and what not.
The Army Corps of Engineers brought out people and built a town at Richland. How quick it was all done is shown by the fact that the sidewalks were essentially tar squeezed out like toothpaste. Cracks would develop in this, and in the cracks asparagus would come up from the asparagus farm that had been there. I think I described about the "sheepherders" who took the Okies and Arkies who came in from the regions where one could get workers, came in on the train to Pasco, Washington about 12:00 or 12:30 at night. The train arrived, and there to meet them were the so-called sheepherders, the people that were ready with buses to bus these potential workers to the working site at Hanford, and the gamblers who were there to lure them off into gambling dens and get away from them any money they had on hand.
There were months of work to do before the construction of the plant could even start. Not only did the city have to be, this town for the Du Pont engineers, but the place for the construction camp had to be set up. Back in Wilmington the drawings had to be made for the plant. Did I go over that at all, the necessity to split the group up into an engineering group, a technical group, a design group, a construction group, an operating group?
Ford: No, not in this series of interviews.
So the technical group would say such-and-such needs to be done and have a sketch of what they had in mind, and then the engineering group would go over it and say, "Well, you've got to change that. We can't have all this welding in the outfit. We have to use bolts or some other way of construction because of the shortage of welders, who are all caught up building ships." And there was a question of getting priorities from the government for getting this, that, or the other material. There was steel or aluminum, so that the engineering group had to deal with things of this sort. It was a popular story that if the cooling design had to be changed to go not from bottom to top but from top to bottom, and you brought this up to the construction group, the construction group would say, "Well, we can't do it." So you keep after them, and then one day you find that they had managed to turn the building upside down in a few days. There was a rumor that the construction workers didn't know what the plant was going to build, but they figured since it was Du Pont it must be nylon stockings, because they saw all the stuff going in and didn't see anything coming out.
FAMILY IN THE WAR YEARS
Ford: What was your chronology? You moved to Chicago with your family in January of '42...
Ford: .and then did you start to visit Han ford for short trips?
First I was visiting Wilmington more and more, and I think it was something like March of '43 before the Wilmington people said, "You better just figure on moving here." It was July of '44 [ when we ] moved to the State of Washington, to Richland.
Ford: You and your family did move back to Wilmington between Chicago and Hanford?
Yes. We had tried at one point to see if we could get Uhlenbeck to join the project. I called him up and [ he said ], "Where is this project?" I said, "Wilmington." He said, "Vilmington? Ver iss Vilmington?" [ laughs ] But he didn't come.
Ford: What was housing like in Hanford when you first went there?
I remember 416 Pittsboro Street was the house we were able to move into. [ This may be a slip of the tongue. This was given as the address of the Chapel Hill house. ] Let's see, was it a one-story house? I guess it must have been two stories. I can recall that when the wind blew the children outside with bare legs would come in crying because the sand cut their legs. And we'd find all the window sills covered with sand. We'd have to wipe them off afterward. There were bathtubs in the houses made of concrete, solid concrete, three or four inches thick, nice cozy thing to get into, [ laughs ] Toward the end of the war, finally, a shipment of real steel bathtubs arrived. They were about to be installed, and then the Columbia River developed a flood. As a quick way to build the dike higher, everything available had to be tossed into the construction of the dike, including the crates in which these new bathtubs were. [ laughs ]
Ford: Was Tita already in school at that time?
Yes. The children went to the school called Sacajawea School. That was named after the Indian guide who had been so useful to the Lewis and Clark Expedition.
DU PONT AND HANFORD
In my role as an advisor to the Du Pont group, I found it necessary to keep in close touch with my colleagues in Chicago. So, typically, I went back and forth once a week to Chicago. During the construction of the plant in the State of Washington, it was also important to keep in close touch with the group in Wilmington, so I typically went back and forth between Wilmington and the State of Washington once a month. I can recall taking a train out of Wilmington to North Philadelphia, then changing there, going under the tunnel, coming up on the southbound track to board the train at 7:19 p.m., going from New York to Chicago on the Broadway Limited, and there taking the Union Pacific, Chicago to Pocatello, Idaho, getting out of the train at Pocatello, and being met by a car there taking me and a couple of Du Pont colleagues across the river to Richland. I can't recall how far that was, but my horseback guess is 50 miles, maybe 70 miles.
One of the colleagues on some of these trips was Charles Cooper, a chemical engineer. His work was absolutely vital in getting a canning for the slugs of uranium to separate them from the water and avoid corrosion of the slug and avoid release of radioactive materials into the water. The canning problem, what alloy to use: Charles Cooper and his gang solved that very difficult problem there. He had been in earlier life many other things, including a licensed Maine Guide. He had given a course—I've forgotten whether it was at New York University or at what school in the New York area—on estimation, and the final examination consisted of a single question, he told me: "How far can a wild goose fly?" If you put in a reasonable estimate as to what fraction of the weight of the goose is fuel and put in an estimate of how far the goose would descend if it were simply gliding so one could see the loss of energy that way, dropping under gravity, and figure how that compared with the distance to be traveled, one would typically come out with a distance of a couple of thousand miles. Another question was: "How many drugstores are there in the United States? Make an estimate of that."
The man in charge of the plant during the period of construction was Walter Simon. He told me about the typical visit of General Groves, General Groves always needling everybody he could, Simon taking him around: "How come you haven't got more of these walls of the reactor plant?" And how come this, and how come you haven't done that, and Walter Simon always responding in a very polite way. And finally at the end of the day Groves exploding at this politeness, "Simon, are you a man or a worm? Can't you speak up?" and Simon saying, "Why General, we have people in Wilmington who can speak up to your questions." [ laughs ]
Safety was a side of the project that I had not appreciated until Du Pont came into it. Having been in the explosive business, they developed a long tradition of operating with special forethought to safety. For example, the different portions of a gunpowder plant in the very early days had been a number of work places separated by stone or masonry walls. Du Pont was accustomed to put a very light roof and very light front on so that if any explosion took place in one of these work areas, it would not be communicated to another; it would just explode out easily. In fact, all my Du Pont friends are accustomed to fastening their seat belts. I think I've written about that in my little book At Home in the Universe, about how the Du Pont... Roger Williams was a person who offered the greatest guidance on this, and he dreamed up the word. He thought that "radiation protection" was not a good word; it produced a negative image in the mind of the workers. So he dreamed up the word "health physics" for this business. I am interested to know that around the world today that's the preferred word.
Well, the question arose, how safe was it to process plutonium? Was not there a chance there might, in one of the process vessels, accumulate too much plutonium and become critical, develop a self-sustaining reaction, spill and make the whole thing radioactive? The building where this chemical processing was conducted was so huge, so many separate portions of the process, so huge that it was called the Queen Mary. And to build another Queen Mary to reduce the amount of plutonium per process vessel by a factor of two would cost something like $200 million and would sew things up for months. I went to Los Alamos to get the latest results on critical masses. Richard Feynman had been involved in that question, and when I got back I recall going over it all with Bill Mackey, who was by this time the plant manager. We decided it was very difficult to put a number to the chance of an accident, but we thought that all reasonable ways of working would cut the chance to a negligible factor. And Bill Mackey said, "Well, we don't have a numerical way to decide this issue. Then we'll have to decide it on the basis of judgment. The reason the Du Pont Company pays me is to make decisions on the basis of insufficient evidence, and I'll decide we won't build another Queen Mary." ( I can't recall whether there were already two and this would have been a third, or whether there was only one and it would have been a second. )
There was so much heavy equipment to be moved to the various sites that a plant railroad was constructed, and it was a great treat for me when one of our friends arranged for me to be taken around on the plant railroad.
I can recall that typically we drove from the technical area near the town of Richland to the plant, a distance of say 30 miles, in a car, and every now and again the car would kill a rabbit. Fermi made a calculation of how many rabbits there must be per square mile based on the speed of the car and the number of rabbits killed.
JAPANESE FIRE BALLOONS
I just came across the other day, and I think I must have put it in the box of our autobiographical materials, the pages I photocopied from a book about the Japanese fire balloons. Somebody at the Smithsonian Institution had done a historical study of these balloons. They were built of paper, filled with hydrogen, launched from Japan, carried by air currents across the Pacific. The timing was such that the fire grenade be dropped, it was planned, on passage over the western United States. So there were any number of forest fires in Oregon, Washington, and British Columbia caused this way. One of these balloons, or rather the ropes dangling from it, became entangled one day, purely by accident, in the power line that fed electric power to pumps on one of the nuclear reactors. As a consequence, the power was cut off for some hours. So this was the only American plant shut down by enemy action during the war.
This was of course before either Hiroshima or Nagasaki. It seems to me this was around October of 1944. I can recall, because I was in an upset state, because word had come that my brother was missing in action in the fighting in Italy. How could we do something to find out what his fate was? I don't know all the long story of how it went from there, but at any rate I visited his grave near Florence, Italy some years later.
But walking with my colleagues from lunch back to the technical area, I recall one of us pointed out and said, "Look, that must be a Japanese balloon up there in the sky," and we all perked up and looked carefully and we finally concluded it was not a Japanese balloon; it was the planet Venus in broad daylight.
LINKS TO LOS ALAMOS
Ford: In your trips to Los Alamos during the war, did you get involved in bomb design work, bomb theory at all?
No, I didn't really. I recall going out on the mesa during an implosion run, but I suppose the closest I recall is this business Richard Feynman described to me of the run on the IBM card programmed computers there of an implosion. It was clear that something was wrong with the computer, because the different layers of metal had such very different velocities. What's more, when they would run it again [ they would ] get different numbers. There was some instability there. He finally concluded not to blame the computers, but to blame the program, because they hadn't put in any mathematical term for energy sucked up in heat in the implosion, and here the computer was doing its best to produce heat by this vibratory motion of one layer relative to another./p>
Gregory Breit had been there, and he had been put up against the question, "When this bomb is set off, is there a chance it might ignite the atmosphere, and the whole planet would go into a thermonuclear reaction?" He and whatever colleague he had on that concluded No, there's no chance of that.
Ford: I think it may have been Konopinski who worked with Breit on that question. I just can't [ remember ]. I'd have to look it up.
Ford: A sidelight question, John. When you took the train from Hanford to Los Alamos, what route did you take? What kind of a trip was it?
Oh, well I was on the train going from Wilmington to the State of Washington, and as I got to Fargo, North Dakota, somebody came on board with a telegram for me from my Du Pont people, saying to get off and take the train back to Chicago and take the Chief there down to Los Alamos. So that was an experience on board the Santa Fe Chief. I can't recall whether it was the Chief or the Super Chief at that moment. It all depended on what your schedule was, which one you managed to get.
I recall that at one point Dale Babcock, the person I worked with most closely at Du Pont, and I had to get east in a hurry from Hanford and a train would not be fast enough, so it was necessary to go on board a plane. Well, in those days you couldn't get on a plane without a special priority, so it took some paperwork to get this priority. We got it, and we arrived at the airport—I've forgotten where the airport was in the State of Washington — and they said, "It's great, but you don't have any reservation." [ laughs ] So somehow we got east.
Ford: That was a commercial flight, not a military flight?
It was a commercial flight, right.
BACK TO HANFORD
Ford: I think it would be very interesting to hear your comments on the tests that led up to criticality for the Hanford reactor and then the final achievement of criticality. We've only got about six minutes left on this tape.
Well, it's wonderful that I came across just while you were away this last week a description by Dale Babcock of all that in a way that I couldn't possibly reproduce.
PERCEIVED JAPANESE THREAT
I've forgotten whether I mentioned that after the Japanese fire balloon there was a great degree of concern about the possibility the Japanese might drop a bomb on the installation, or somebody, the Germans, so that all the airports within some hundreds of miles of Richland were checked out. There was a radar that kept giving indication of something flying overhead at night. But where did this come from? Then finally, after immense work checking out conceivabilities, it turned out to be just the wild ducks.
But somehow the threat of those fire balloons percolated in a subterranean way around the community. My boy, Jamie, came into the house and asked his mother if he could go with the other boys across the river and see these Japanese, their fire balloons. How come? "Well, all the boys were talking about it," he said. So she said, "I'll call up the police, and if they say it's okay, you can go." She called up the police and they didn't just laugh it off. They evidently were tuned in and took it seriously.
INSIGHTS ON JAPANESE CAPITULATION
Speaking of the Japanese, there is a book by Haru Matsukata Reischauer, the Japanese wife of the American Ambassador who came from a distinguished Japanese family — two families of course. The book is called Samurai and Silk. The last chapter in that book is about the member of her family who had been with the Imperial Court in Tokyo — how the Cabinet would meet and come to a decision and make a recommendation to the Emperor. Since it was unanimous, you will always have to just check it. But after the Hiroshima bomb, they didn't immediately come to the Emperor. They didn't come to him until the next day. But by then they had argued themselves into saying they were going to go on with the war, so it was a unanimous decision to go on with the war. Well the Emperor was very angry with them, because they had waited a whole day to let him know about this tragedy. Well, when the next bomb fell, the Cabinet came to him divided, 50 [ percent ] for going on with the war and 50 [ percent ] for surrendering. At last he entered a voice and he said to give up. But it's one thing to say that to the Cabinet and another thing to get it carried out. Before he could do that, the guard in the garrison right next to the Imperial headquarters heard about this, and they were opposed to giving in, and they staged a coup. They took over the Imperial headquarters and they cut all the phone lines to the outside, or so they thought. But they didn't realize that their navy had installed a line which gave access to the outside, and with that the Imperial party reached a military center and they got a group that came in and put down the coup, and the three leaders had to commit hara kiri.
PHYSICS DURING THE WAR
My bibliography unfortunately does not include more than two or three of the reports written in Chicago and Wilmington days.
I recall the stimulus of Fermi's presence at Richland. He was already thinking about how to get back to particle physics. And I must have been stimulated by word of the New York Academy of Science's prize award [ contest? ]. Anyway, I sent in a paper for it, a paper on polyelectrons, objects made out of positive and negative electrons, the simplest being just a super-light hydrogen atom, then after that a super-light hydrogen ion, and after that more complicated systems. I can't recall if that paper also discussed the annihilation of the positive and negative electron and the relative polarization of the two photons given out in that annihilation process. I know that there's a correction I should put in that calculation, but that's the process that John Bell made, later on, the center of attention in talking about the implication of quantum mechanics.
It seems to me it must have been about this time that Fermi wrote a paper on the mechanism by which cosmic rays are accelerated. He dealt with the physics of a cloud of ions in space. That cloud of ions has a kinetic energy and also, by virtue of traveling through a region with a magnetic field, has a potential energy. He argued on grounds of equilibrium in order of magnitude between kinetic and potential energy. [ He wrote ] about this mechanism and how it provided a way to get high-energy cosmic ray particles.
COSMIC RAYS AND ELEMENTARY PARTICLES
I confess that I couldn't help feeling that the big mystery in the future would be associated with these particles and that to get into the field in any practical way, any economical way, you'd have to do it by cosmic rays. So already before I got back to Princeton I was talking about using or taking over the high-explosive laboratory that Walker Bleakney and his colleagues had set up, taking that over to use after the war for cosmic-ray physics. I think I called it, however, elementary particle physics. Various Du Pont friends got together and got up a sum of money to be used to assist in starting elementary particle physics work at Princeton. I think they were called Friends of Elementary Particle Physics. I'm afraid we've used up that fund by now.
If an already used laboratory was to be the center for this work, then also the people with whom we started were people who had already been used. There was W. Y. Chang, Chinese, and there was Thorbjorn Sigurgeirsson from Iceland, as specially qualified physicists to begin. There is a lovely account of Sigurgeirsson's later on in life saving Iceland's lone south coast port from being overwhelmed by lava flow by spraying water on the lava, in a book by John McPhee.
How to get the particles to work with? Well, the cosmic rays offered them. Chang put plates of lead or other materials in their way, and with a counter above tike plate to record the arrival of the particle and a counter below to show that no particle had come out, could have a system that would respond to particles that stopped in the lead. Then also a way to detect gamma rays, and in this way [ he ] detected gamma rays from the dropping of mu mesons from one Bohr orbit around the lead nucleus to another Bohr orbit. I wanted to get this radiation called the Chang radiation, but the name didn't stick.
Ford: The paper on that subject by Chang in Reviews of Modern Physics, and Sigurgeirsson, helped these experiments.
Chang was separated by the exigencies of the war from his wife, who had been working with Uhlenbeck at Michigan. During the war they would occasionally meet at some intermediate point. It might have been Indiana. But after the war, as loyal Chinese, they returned to China. She taught physics at Peking University and he ultimately became—he had the nuclear physics section of I'm not quite sure what. For a time one of them was working at the Russian nuclear laboratory at Dubna near Moscow, and they had the same problem they had in the United States of being able to get together only occasionally.
Ford: John, were you the first to suggest that this Chang radiation could be used to measure the size of the nuclear charge distribution?
Yes. There was a paper I put together about this time, if I could find that — oh yes, "Mu Meson as Nuclear Probe Particle" — to explore the size of the nucleus. That was a useful article, I believe, judging by the amount of response I got from it. Another article at that time: I was invited by the American Philosophical Society to give a talk, which I put under the title "Problems and Prospects in Elementary Particle Research," which laid out a bit of a program for the future. That was in 1946.
By 1947, I had been entranced once again with how much one can do with the Correspondence Principle, principle of correspondence between classical and quantum theory, and was using that to help understand features of the process by which an atomic system emits a pair of photons, double-photon emission.
John Shanley, if I remember right, had been one of the members of the Project Matterhorn thermonuclear project. He and I and Evan Kane got interested in the effect of planetary magnetic fields on access of cosmic rays to the Earth's surface. We already knew from the work of Compton that the Earth's field was very important in limiting the energy of cosmic rays and the direction in which they come to the earth's surface. That was one of the payoffs of the debate between Compton and Millikan. Kane and Shanley and I were interested in how the magnetic fields of other objects circulating around the sun could affect the spectrum of cosmic rays coming in. I can't recall anything having come out of that that was, as the saying goes, both new and true.
We knew that the stopping of mesons in lead plate as shown in the experiments of Chang and Sigurgeirsson sometimes had to do with the mesons which simply decayed essentially in the loose material. How to understand that spectrum? And there we were forced to say that a neutrino had to be given out with the electron to understand why there was a continuous spectrum. But I don't think we were anywhere near the first to suggest that when a mu meson is stopped near the nucleus, there is more than straight decay of the mu meson that can occur. It can interact with the nuclear particle. For example, a negatively charged mu meson can interact with a positively charged proton to give a neutron plus a neutral particle—a charge exchange reaction. I think it was in that paper that we put forward the so-called triangle relation between the coupling of three kinds of reactions—later ( I hope I'm correct on the timing ) called the Puppi Triangle.
If I get some more time, I'll try to put together the case why Tiomno ought to get an award for that work of his, because he is one of the most unappreciated people in the field of physics.
COPENHAGEN IN 1951
About this time I found myself made one of the U.S. representatives on the International Union of Pure and Applied Physics. I recall going to Copenhagen and being told that I was expected to put on a party for the other people. There was a very limited amount of money, and how to do this was quite a challenge in a foreign city. But it turned out that the sister of the American Ambassador was visiting, and [ there was ] nothing that she would enjoy more than putting on this party. So we turned over to her the money that would otherwise have been spent, and with the help of that money and the normal Embassy facilities, why a very nice time was had by all who came. That was 1951.
It was at that time that my wife and I one evening in a restaurant looked up and saw somebody had come in, sat down all by himself at a table. He looked a bit familiar, and after a while I realized it was Heisenberg. So we invited him to come over and sit with us.
POST-WAR WORK ON FISSION
About this time I was invited to do a paper for the Annual Review of Nuclear Science on nuclear fission and nuclear physics. I was trying to fit this into the time squeezed out on the H bomb project. I can recall trying to keep awake in the evening to work with David Hill, taking a bath and getting up and going on. But when the paper finally got in to the Annual Review, it was regarded as too long and too late, so I submitted it to the Physical Review and Sam Goudsmit accepted it. But some kind member of his staff rearranged it, unfortunately for me—to assist the printer, all the pictures were put at the end of the article instead of being scattered through the article where they could best illustrate the subject. That paper was the place where the collective model of nuclear structure, what [ Aage ] Bohr later called the unified model, got its first run for its money. Later, in 1953, the same idea was presented in briefer form at a conference in Japan.
RELATIVITY COURSE AT PRINCETON
November 1st, 1952 was the test of the Mike H bomb. I can remember flying the helicopter over the waters surrounded by Eniwetok atoll and looking down at the sharks circling underneath and feeling they were a greater source of danger than what would happen to this H bomb.
But I was already eager to get back to pure physics and had asked Shenstone, by that time the Chairman of our physics department, if I could give a graduate course in relativity. I evidently already realized at that time the reason universities have students is to teach the professors. It was a great thing to give that course and learn about gravitation, and one of the outcomes of it was a model of something particle-like and yet not a particle: a geon, a gravitational wave going around in a circle held in orbit by the mass-energy of that wave itself. It could be a gravitational wave or electromagnetic wave or some mixture of the two. These geons, however, interesting though they were in their own right, could hardly be regarded as a model for elementary particles.
WORK WITH LAMB ON COSMIC-RAY ELECTRONS
Willis Lamb and I had written, years earlier, a paper on the effect of atomic electrons on the field of force that a high-energy electron experiences as it zooms down through the atmosphere. This screening by the atomic electrons reduces the sphere of action of the field of the nucleus and means a diminished amount of radiation by a high-energy electron passing down through the atmosphere, and also a diminished probability to produce a pair. Lamb and I calculated this effect of atomic electrons on radiation and pair production. That was in 1939, and in a 1956 paper we published a correction to the scale. Somehow we had not put in the correct scale.
The attention of the elementary particle physics community at this time had gone largely to vacuum polarization — that is to say, the effect used to explain the Lamb shift. Will it come into play in a wider domain? I wondered. Is there a broader way to understand it? Yes, it can be encompassed through causality. Bob Euwema and I worked on this.